Various techniques for making measurements of a ship's speed through the water have been used over the years by mariners. However, the known techniques have either lacked sufficient accuracy to evaluate a hulls efficiency, or they have required undesirable instrumentation installations on the ship.
It is an object of this invention to provide a means of accurately determining the speed of a ship through the water which makes use of accurate instrumentation that does not require extensive shipboard installation.
Some of the prior techniques which have been employed have made use of a Doppler type speedometer which has the drawback of being subject to difficulties with surface water effects. Another technique has made use of Pitot tubes, but that has relatively poor accuracy. And, it is subject to changes in the indications with a ships trim.
Consequently, it is another object of this invention to provide for a method and system that is accurate and yet simple to carry out. It employs a free floating buoy and uses a pair of tracking scopes. Relative movement of the buoy and ship are accurately measured over a known distance, with the time of travel being electronically measured and so having high accuracy.